Stuggling to cancel contract

I have an account with MTN with 3 contracts on. On 29 Dec 2015 I phoned the call centre to cancel all three contracts as the 2yr contract is over. I spoke to a Dennis and he assured me that he will send a mail to 'the people who deal with cancellations'. Today, I receive a new account statement. I phone the call centre again and apparently they have no record of me calling on 29 Dec and my contracts are still NOT cancelled. Again an e-mail will be sent. Two of the contracts I wanted to cancel since the beginning of last year. Same old story month after month. And every time I have to tell a new person the same story over. Apparently all supervisors are in meetings the whole day long. I have had enough of this and I am done with MTN.